With many thanks to David Tesar, the updated Silverlight Enterprise Deployment Guide was published recently.
Read David's post announcing the guide.
There's a link to the guide on David's blog or on the Administration resources page on the Microsoft Silverlight website.
Refer to this guide for answers to all your questions about enterprise deployment of Silverlight via WSUS, SCCM, Group Policy, etc...
The original guide was written for Silverlight 1.0. The changes between Silverlight 1.0 and Silverlight 2 warranted an update to the guide but we didn't update it for Silverlight 2 RTM right away because we knew there were more changes coming.
To make the new guide more useful and more long lasting we backported all the changes we were making for Silverlight 3 into the update to Silverlight 2 that we shipped a couple months ago. So, the good news is that this update to the guide applies equally well to the current release of Silverlight 2 and to the upcoming release of Silverlight 3! So, you can comfortably get started on deployment planning based on Silverlight 2 and then easily swap out Silverlight 3 when it is released without a full reset of your efforts.